This invention relates to an intake system for a multi cylinder engine and more particularly to an improved induction system that improves low speed running performance and also which does not sacrifice high speed performance or running in the midranges.
One form of induction system for an internal combustion engine that has particularly advantageous high speed performance employs a separate intake passage for each combustion chamber of the engine with a throttle valve that is positioned relatively close to the combustion chamber for controlling the flow through the respective induction passage. With such an arrangement, it has been proposed to provide a pressure regulating tank that communicates with the induction passages between the throttle valve and the combustion chamber and which incorporates a control valve that controls the communication of the pressure regulating tank with the induction passages In such a system, the opening of the control valves is increased during low speed operation when the throttle valve opening is small, particularly at idling, so that each intake passage communicates with the pressure regulating tank so as to reduce pressure fluctuations and variations in mixture concentration within the intake passage. This has been found to stabilize combustion and improve low speed running. To avoid deterioration and high speed output, it has been proposed to reduce the opening of the control valve under high speed operation, thus improving the responsiveness of the throttle control of the engine.
Another form of device has employed a bypass passage that communicates the intake passages with each other across the throttle valve and in which a control valve is positioned so as to control the idle speed by varying the opening of the control valve at such times as when the throttle valve is closed or in its idling position.
Although the aforenoted constructions can improve engine performance, the number of the passages employed and the sequences of opening and closing of the valves in them can be critical of engine performance and also can add significantly to the cost of the induction system.
It is, therefore, a principal object of this invention to provide an improved induction system for an internal combustion engine.
It is another object of this invention to provide an induction system for an internal combustion engine that employs a bypass system for the throttle valve of the induction passage and which will improve running at low speeds and will not deteriorate high speed performance.
It is a further object of this invention to provide such a control system for a multiple valve engine wherein the arrangement can be generally simplified.